The poly(ADP-ribose) polymerases (PARPs) form a family of enzymes with roles in DNA repair and apoptosis, particularly in response to reactive oxygen and nitrogen species. PJ-34 is an inhibitor of PARPs which can be used in cells or in animals. It binds and inhibits the PARP tankyrase1 (IC50 = 1 μM). PJ-34 also inhibits matrix metalloproteinase-2 when used at higher concentrations (IC50 = 56 μM).